It is known from EP-A-0898245 to process images of the object taken from different, unknown positions using a matching process in which points in different images which correspond to the same point of the actual object are matched, the matching points being used to determine the relative positions and orientations of cameras from which the images were taken and to then generate model data. This process of determining the camera positions is referred to as calculating a camera solution and EP-A-0898245 discloses a camera solution process relying upon epipolar geometry between virtual image planes of cameras at camera positions from which corresponding images were obtained.
Having solved the camera positions and orientations for an initial three cameras corresponding to an initial three images in a sequence of camera images using a first solution algorithm, EP-A-0898245 teaches that each new image of the sequence of images requires its camera solution to be obtained using a second camera solution algorithm which assumes the camera solution for the preceding image in the sequence to be accurately known from previous calculations. Matching points between the new image and the preceding images in the sequence may then be processed to accumulate further model data.
This known method of camera solution, referred to below as a 2-D to 2-D camera solution process, effectively takes as a starting point pairs of co-ordinates in virtual image planes of a pair of virtual cameras in the three-dimensional model space and calculates the parameters defining the position and orientation of each camera based on these pairs of two-dimensional image co-ordinates for matching points.